dispersal of ticks and tick borne diseases by birds - Lista fuglestasjon

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migratory birds were examined with PCR by the same method as used by Lundsett and found A. phagocytophilum in 13.1%. The findings were not confirmed by sequencing and were not published. This pathogen is established in most areas where I. ricinus is prevalent (Stuen and Bergström, 2001), and cervid animals represent a much more effective means of spreading ticks on the mainland and to coastal islands than birds; therefore, it seems reasonable to assume that the birds’ contribution to spreading this ubiquitous pathogen has little biological significance, unless subgroups of different virulence exist. The situation is completely different for B. divergens, which has become rare in some parts of the Norwegian coast (Paper IV). Possible explanations for this decline are changes in the use of pastures, and effective chemotherapy. The possibility that birds may reintroduce this parasite must be taken into account. A PCR with a primer specific for the B. divergens group (Lundsett, 2004) was performed on 511 nymphs from northward migratory birds, and B. divergens was found in 1.2% of them (unpublished results). Other Babesia spp., e.g., B. microti and B. bovis, occur in Europe (Meer-Scherrer et al., 2004) but have not been found in Norway. B. canis has recently been found in Norway for the first time (Øines et al., 2010). These Babesia spp. have not been included in this study. For B. canis, which has Dermacentor reticulatus as its main vector, the finding of a Dermacentor larva on a willow warbler (Phylloscopus trochilus) at Akeröya (Paper III) is of special interest. In Paper IV, the occurrence of antibodies against the bovine pathogen B. divergens in pasturing cattle along the southern Norwegian coast was examined. This pathogen is now a limited problem within its distribution range in southern Norway, but has the potential of reemergence if letting cows pasture in the woods is recommenced. A high fraction of cows (median about 50%) in the 38 western part of West Agder and in the eastern part of East Agder and in Telemark had antibodies against B. divergens, as opposed to a median of about 5% positives in the area between (Figure 2 in Paper IV). The areas where the fraction of Babesia-positive cows is high fit with the areas where the bird observatories are situated. Bird migration corridors could explain the high prevalence of B. divergens in cows in these areas, but there are no scientifically controlled data confirming that there are more migratory birds in these areas. Although an important issue, the ticks in this study were not examined for TBEV. Four of the bird observatories in the study are situated on islands, and freezing and transport of frozen material for RNA-PCR would be difficult to carry out. Additionally preservation in 70% ethanol is a good method for keeping the ticks for later species identification, which could not be performed at the bird observatories. However, a Swedish group have examined ticks for TBEV (Waldenström et al., 2007) and they found TBEV in 2/529 larvae and 4/409 nymphs. TBE is an emerging disease in Norway; the first case was reported in 1998 (Skarpaas et al., 2002; 2006). The distribution is discontinuous with the rest of the distribution area of TBE in Europe. Between one and four million Sylvia warblers migrate to Norway each spring and bring ticks (Paper III). Many of these migrate across TBE-endemic areas in Central Europe before arriving in Norway. To bring TBEVinfected ticks from Central Europe to the endemic areas in Norway the birds have to cross at least 400 km of land and at least 112 km of open sea. This is barely possible: Although the maximum speed for the garden warbler, Sylvia borin, is 291 km per day, the mean speed of migration is 50 km per day, and I. ricinus larvae and nymphs remain on the host for just 3-4 days. A total of 835 northward migrating Sylvia warblers from 2003 and 2005 were examined, and 38 larvae (0.046/bird) and 63 nymphs (0.075/bird) of I. ricinus were found feeding on the birds. These species would, be expected to carry 45,000-180,000 larvae and 75,000-300,000 nymphs to Norway every year, but just a
small fraction of these would be transported from TBE-endemic areas. TBE is maintained in nature by a fragile enzootic transmission cycle (Randolph and Rogers, 2000), when larvae contract the virus by co-feeding with TBEinfected nymphs on small rodents. The transovarial transmission of TBEV is low: only about 2.4-7.8% of larvae born from an infected female are themselves infected (Danielová and Holubová, 1991; Randolph, 2008). Therefore, questing larvae of I. ricinus rarely carry TBEV. Considering the large number of larvae imported, there is a possibility that birds can import TBEV-infected tick larvae, which, after moulting to nymphs, could spread the virus further to local larva. Furthermore, infected nymphs imported to Norway could mature to the adult stage, and by transovarial transmission give birth to TBEVinfected larvae. Therefore, it is a small possibility that birds could spread TBEV, and it is difficult to imagine any other way the virus could have reached the southern Norwegian coast. Although the enzootic transmission cyclus is fragile, a climate model predicting the distribution of TBE (Randolph 2001) indicated favourable conditions at the Agder coast. Therefore, in principle, one single TBEV-infected tick could introduce the disease. The next question would be: why has this not happened before? TBE may well have been unrecognised in Norway for many years, and it may have died out because of the fragile enzootic transmission cyclus and been reintroduced by birds, or it may have been introduced during the last decades because TBEV is increasing in Europe. Traavik et al. (1978) reported TBEV in ticks from Western Norway, but this may have been LIV, as the identification was made by immunological methods. Traavik (1979) also found TBEV-antibodies in 19.6% of humans living in areas where I. ricinus occurs in Western Norway, but this may be due to cross-reacting antibodies. One Norwegian woman (a patient of Gunnar Hasle) had serous meningitis when she 39 lived in Risør (at the coast of East Agder, Norway) in 1987. At the time she had not been in any known area where TBE occurs, but Risør is at the coast of Aust Agder, near areas where TBE has later been found, and where LI has not been reported. She was examined at Ullevål University hospital for sequelae and was tested for TBE-antibodies in 2001. TBEV IgG was strongly positive. She had not had any other meningitis or encephalitis since 1987, and had not been in any area where TBE is known to occur. This may be the first case of TBE in Norway, although the first officially notified case was in 1998. The role of birds in the epidemiology of TBE is still unknown. It has been isolated from I. uriae and tissue from guillemot (Uria aalge) in the Murmansk area (Chastel 1988). LI, which is closely related to TBE and may cause disease in humans (Davidson et al., 1991), has been found in Western Norway (Stuen 1996). Nucleotide sequence analyses indicate that LIV has been recently transported to Norway from the British Isles (Gao et al., 11993).) An alternative explanation to transport by birds is that TBEV has existed in the Scandinavian peninsula since Sweden and Denmark were connected 8-9,000 years ago (Björck, 1995) and that the virus has lived unrecognised in a zoonotic cycle. Phylogenetic analyses indicate time points of divergence of W-TBEV and FE-TBEV of 400 and 600 years before present (Zanotto, 1996; Haglund, 2000), which indicates a much more recent exchange of genetic material across the sea. The TBEV strain found in Norway is phylogenetically closely related to the strains found in northern continental Europe (Skarpaas et al., 2006). This study has not proven that birds have introduced TBEV to Norway, but it can be concluded that it is possible that such transport has happened and that this is the most parsimonious explanation for the existence of TBEV north of the Skagerrak Sea. Originally, the blood sampling from dairy cows (Paper IV) was intended to be a study of mapping the distribution of TBEV by
Page 1 and 2: From Dept. of Biology, University o
Page 4 and 5: There are three rules for writing t
Page 6 and 7: TABLE OF CONTENTS Table of Contents
Page 8 and 9: 6 ABSTRACT Hard ticks (Ixodidae) ar
Page 10 and 11: LIST OF PAPERS. I. Røed, K.H., Has
Page 12 and 13: 10 NDVI Normalised Difference Veget
Page 14 and 15: BACKGROUND Box I Some Ixodid ticks
Page 16 and 17: cattle are in some areas commonly a
Page 18 and 19: fourth feeding experiment, a mean f
Page 20 and 21: seen in I. ricinus that had fed on
Page 22 and 23: explained by a change in the true t
Page 24 and 25: LITERATURE ABOUT TICKS ON MIGRATORY
Page 26 and 27: air is plotted for certain times an
Page 28 and 29: ETHICAL ISSUES This is a descriptiv
Page 30 and 31: were picked off by a blunted clockm
Page 32 and 33: SYNOPSIS Paper I: Primer note. Iden
Page 34 and 35: GENERAL DISCUSSION Hubálek (2004)
Page 36 and 37: (AVHRR) of the National Oceanic and
Page 38 and 39: discovered on the horse four months
Page 42 and 43: using cow sera, and to see if this
Page 44 and 45: ACKNOWLEDGEMENTS Thanks to my three
Page 46 and 47: Brown, D., 1997. Dynamics and impac
Page 48 and 49: V.A., Gould, E.A., 2003. Characteri
Page 50 and 51: Kurtenbach, K., de Michelis, S., Et
Page 52 and 53: Perret, J.-L., Guigoz, E., Rais, O.
Page 54 and 55: irds. Journal of Infection. 56(2),
Page 56 and 57: Figure 2. Unrooted phylogenetic tre
Page 58 and 59: 56 Figure 5. Example of a wind traj
Page 60 and 61: 58 Figure 7. A female red-backed sh
Page 62 and 63: Figure 10. Blood sampling from the
Page 64 and 65: Table 1. Estimated numbers of Norwe
Page 66 and 67: 64 Table 4. Previous studies on tic
Page 68 and 69: Spørreskjema til kubønder på sø
Page 70 and 71: INDEX A. phagocytophilum...........
Page 77 and 78: 345 J. Parasitol., 94(2), 2008, pp.
Page 79: esist the immune responses of hosts
Page 83 and 84: TRANSPORT OF TICKS BY MIGRATORY PAS
Page 85 and 86: 1344 THE JOURNAL OF PARASITOLOGY, V
Page 91 and 92:
1350 THE JOURNAL OF PARASITOLOGY, V
Page 95 and 96:
Hasle et al. Acta Veterinaria Scand
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103:
Page 108 and 109:
Transport of Ixodes ricinus infecte
Page 110 and 111:
ird taxa contribute to the spread o
Page 112 and 113:
Results We detected Borrelia in 70
Page 114 and 115:
The number of Borrelia-infected tic
Page 116 and 117:
carrying infected ticks, the travel
Page 118 and 119:
Jenkins, A., Kristiansen, B.E., All
Page 120 and 121:
*Detailed Response to Reviewers Osl
Page 122 and 123:
The interaction between cofeeding a
Page 124 and 125:
Table Table 2. Borrelia-spp. as det
Page 126 and 127:
Table Table 4. Logistic regression
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